Nearly every steering wheel unit of a motor vehicle includes an airbag module. As a rule, the steering wheel unit includes a steering wheel body and an airbag module accommodated in the hub region of this steering wheel body. The airbag housing of the airbag module is covered by a cover that forms one part of the surface of the steering wheel. As a rule, the surface of the cover also serves as an actuation surface for the car horn such that when a force that exceeds a predetermined value is exerted on the cover, the horn is activated. Here there are in principle two known concepts, i.e. the so-called “floating cover” concept, wherein the housing is rigidly connected to the steering wheel body, and the cover can be pressed down relative to the housing and relative to the steering wheel body; and the so-called “floating module” concept, wherein the cover is rigidly connected to the housing, and the cover, along with the housing, can be pressed down against the steering wheel body, the housing and the steering wheel body being connected to each other by horn springs. Recently, stationary or nearly stationary systems have also become known, which do not have any horn springs, but rather wherein the housing, with a corresponding force transfer, is not moved at all, or practically not at all, against the steering wheel body. In this case, the classic horn contacts are replaced, for example, by piezo-electric elements.
In the case of the aforementioned floating-module steering wheel units, positioning units are provided that position the airbag housing in both axial direction and in the radial plane on the steering wheel body. For example, with the above-mentioned type, separate first positioning units are provided for this purpose, which serve the purpose of axial positioning, and second positioning units, which serve the purpose of positioning in the radial plane, are provided. In the aforementioned document of the above-described type, three second positioning units are also provided, wherein each of these second positioning units is constructed as follows: from the bottom of the airbag housing, a pin serving as a positioning element extends in axial direction, the outer surface of the pin serving as contact surface. This pin extends into a through-hole through a component of the steering wheel body, the inner surface of which body forming the opposing contact surface for the contact surface. Due to production tolerances, it is practically impossible to avoid providing a degree of clearance between the contact surfaces and the opposing contact surfaces, which in turn can lead to noise generation and of the contact surfaces and the opposing contact surfaces.
With this as a starting point, the object of the present invention is to improve a steering wheel unit of the above-described type in such manner that the positioning accuracy is improved and ideally, zero backlash is achieved between the contact surfaces and the opposing surfaces of the positioning unit (non-axial positioning unit). Furthermore, in so doing, the functional reliability of the steering wheel is to be ensured, even when the gas generator is activated.